Services for distributing content, such as a television program or a movie, via a network, such as typically the Internet, have been realized using unicast distribution (refer to, for example, Patent Literature 1).
FIG. 1 illustrates an example of a configuration for realizing unicast distribution. Unicast distribution is realized in the following manner. Each of terminal devices 4 accesses a distribution server 1 via the Internet 2 and requests the distribution server 1 to distribute content. Thereafter, upon receiving each of the requests, the distribution server 1 distributes content to the terminal device 4 via the Internet 2. That is, in unicast distribution, the distribution server 1 and each of the terminal devices 4 performs peer-to-peer communication. In such a case, as the number of terminal devices 4 increases, the processing load of the distribution server 1 increases and, in addition, data communication traffic of the network 2 increases.
To decrease the processing load of the distribution server 1 and the communication traffic of the network 2, a router 3 of each of ISPs (internet service providers) that constitute the Internet 2 can cache content. In addition, IP multicast distribution that allows content to be multicast (broadcast) or overlay multicast distribution can be employed.